Purpose: The purpose of this study was to investigate the discriminative role of transvaginal ultrasonography and Doppler measurements on the detection of endometrial pathologies in tamoxifen-treated breast cancer patients. Methods: Tamoxifen-treated breast cancer patients were included in this prospective study between February 2009 and June 2010. The subjects were assessed by gynecologic examination and transvaginal gray-scale and Doppler sonography. The patients whose endometrial thicknesses were more than 6 mm underwent endocervical/endometrial curettage for histopathological examination. Results: There were 98 tamoxifen-treated patients with breast cancer enrolled in the study, providing 141 ultrasound evaluations. Uterine artery pulsatility index was significantly lower in postmenopausal than premenopausal patients (p: 0.013). Endocervical and endometrial curettage was performed in 52 patients. It was more prevalent that the endometrial strip was ≥6 mm in women with abnormal endometrial histopathology (p: 0.020). However the women with abnormal endometrial histopathology presented lower vascular indices; the only significant difference was in myometrial pulsatility index (p: 0.036). Conclusion: The most evident tool for evaluating the endometrium in tamoxifen-treated breast cancer patients is still the transvaginal measurement of its thickness. It exists that Doppler ultrasonographic assessment of uterine, radial and spiral vasculature has no additional benefit for detection of endometrial pathology.